Dynamics of efferent control of muscular contraction. Determination of transition processes: External load ? Muscle length

1986 ◽  
Vol 17 (3) ◽  
pp. 238-246 ◽  
Author(s):  
A. I. Kostyukov
Keyword(s):  
External Load ◽  
Muscle Length ◽  
Muscular Contraction ◽  
Transition Processes ◽  
Efferent Control

scholarly journals Oxaliplatin neurotoxicity of sensory transduction in rat proprioceptors

2011 ◽  
Vol 106 (2) ◽  
pp. 704-709 ◽  
Author(s):  
Katie L. Bullinger ◽  
Paul Nardelli ◽  
Qingbo Wang ◽  
Mark M. Rich ◽  
Timothy C. Cope
Keyword(s):  
Action Potentials ◽  
Muscle Length ◽  
Sensory Transduction ◽  
Muscle Stretch ◽  
Functional Deficits ◽  
Oxaliplatin Treatment ◽  
Sensory Encoding ◽  
Dying Back ◽  
Striking Contrast

Neurotoxic effects of oxaliplatin chemotherapy, including proprioceptive impairments, are debilitating and dose limiting. Here, we sought to determine whether oxaliplatin interrupts normal proprioceptive feedback by impairing sensory transduction of muscle length and force by neurons that are not damaged by dying-back neuropathy. Oxaliplatin was administered over 4 wk to rats in doses that produced systemic changes, e.g., decreased platelets and stunted weight gain, but no significant abnormality in the terminal ends of primary muscle spindle sensory neurons. The absence of neuropathy enabled the determination of whether oxaliplatin caused functional deficits in sensory encoding without the confounding issue of axon death. Rats were anesthetized, and action potentials encoding muscle stretch and contraction were recorded intra-axonally from dorsal roots. In striking contrast with normal proprioceptors, those from oxaliplatin-treated rats typically failed to sustain firing during static muscle stretch. The ability of spindle afferents to sustain and centrally conduct trains of action potentials in response to rapidly repeated transient stimuli, i.e., vibration, demonstrated functional competence of the parent axons. These data provide the first evidence that oxaliplatin causes persistent and selective deficits in sensory transduction that are not due to axon degeneration. Our findings raise the possibility that even those axons that do not degenerate after oxaliplatin treatment may have functional deficits that worsen outcome.

Time-varying myocardial elastance of canine left ventricle

1991 ◽  
Vol 261 (5) ◽  
pp. H1554-H1562
Author(s):  
K. Takeda ◽  
R. Kadota ◽  
S. Yagi
Keyword(s):  
Left Ventricle ◽  
External Load ◽  
Muscle Length ◽  
Left Ventricular ◽  
Length Ratio ◽  
Time Varying ◽  
Shortening Velocity ◽  
Bridge Model ◽  
Shortening Deactivation ◽  
Predicted Values

A formula was derived from an active cross-bridge model for expressing the "time-varying myocardial elastance" of the left ventricular (LV) wall. To assess the validity of this model's predictions of the behavior of the intact left ventricle, eight healthy beagles were instrumented with ultrasonic crystals to measure LV diameter and a micromanometer for LV pressure measurement. During ejecting beats starting from short end-diastolic myocardial lengths, the predicted values for myocardial elastance and force closely approximated the measured values for the instantaneous external load-muscle length ratio and the external load, respectively. However, in cycles starting from long end-diastolic lengths, the predicted myocardial elastance and force values deviated from the actual values during the shortening phase of LV contraction. The differences between myocardial elastance and external load-muscle length ratio as well as those between force and external load during the shortening phase (shortening deactivation) appeared to result from an internal load in the shortening myocardium that was closely related to the product of instantaneous myocardial force and shortening velocity. Thus this model may provide reasonable approximations of myocardial elastance and force in the intact LV wall. In addition, time-varying myocardial elastance might reflect time-dependent changes in calcium activation.

In situobservation of morphological changes of γ′ precipitates in a pre-deformed single-crystal Ni-base superalloy

2011 ◽  
Vol 44 (5) ◽  
pp. 935-944 ◽  
Author(s):  
Pavel Strunz ◽  
Gerhard Schumacher ◽  
Hellmuth Klingelhöffer ◽  
Albrecht Wiedenmann ◽  
Jan Šaroun ◽  
...  
Keyword(s):  
External Load ◽  
Morphological Changes ◽  
The Past ◽  
Subsequent Heating ◽  
Detailed Evaluation ◽  
The Matrix ◽  
Base Superalloy

Exposure of a superalloy to an external load results in anisotropic coarsening of the γ′ precipitates, so-called rafting. It was reported in the past that γ′ rafting can also occur as a result of purely thermal treatment, without the simultaneous presence of an external load, if the specimen has been pre-deformed at relatively low temperature. The evolution of γ′ morphology in pre-deformed specimens of SCA425 Ni-base superalloy was examined in the present study. Unlike in the previous experiments, the compressive stress was used for pre-straining.In situsmall-angle neutron scattering (SANS) was employed, which enabled the determination of the morphology directly at high temperature. Both for strong and for weak pre-straining, rounding of the originally cuboidal precipitates towards an ellipsoidal shape on heating was observed. Weak pre-straining (0.1, 0.5%) does not cause rafting on subsequent heating. On the other hand, the detailed evaluation of SANS data provides some indication of rafting during the subsequent heating after severe compressive pre-straining (2%). The experiment indicates the role of dislocation rearrangement at the matrix/precipitate interface during pre-straining.

Influence of External Loads on Thin Film Cracking

2004 ◽  
Author(s):  
Srinath S. Chakravarthy ◽  
Eric H. Jordan ◽  
Wilson K. S. Chiu
Keyword(s):  
Thin Film ◽  
External Load ◽  
Crack Arrest ◽  
External Loading ◽  
Element Analysis ◽  
Film Cracking ◽  
Two Parameters ◽  
Improved Accuracy ◽  
External Loads

Cracking in thin films under the combined influence of residual stress and an external load is examined. An improved accuracy version of the existing solution for substrate cracking absent the external load is provided. A superposition scheme that uses the solution for substrate cracking and other existing published solutions is presented for the determination of the energy release rate. The superposition scheme is validated using finite element analysis, and conditions under which the superposition scheme is valid are discussed. Crack arrest is examined and two parameters that determine the possibility of crack arrest are identified. The influence of external loading on channelling behavior in the substrate is discussed.

Peripheral factors influencing expression of pressor reflex evoked by muscular contraction

1985 ◽  
Vol 58 (5) ◽  
pp. 1676-1682 ◽  
Author(s):  
G. A. Iwamoto ◽  
B. R. Botterman
Keyword(s):  
Muscle Mass ◽  
Fiber Type ◽  
Muscle Tension ◽  
Muscle Length ◽  
Muscular Contraction ◽  
Type I ◽  
Active Muscle ◽  
Type Composition ◽  
Slow Twitch Muscle ◽  
Pressor Reflex

The effect of evoked muscle tension, active muscle mass, and fiber-type composition on the pressor reflex evoked by muscular contraction was examined in decerebrate and anesthetized cats. Muscular contraction was induced by stimulating the L7 and S1 ventral roots with 0.1-ms duration pulses three times motor threshold at various frequencies. The experiments were designed to isolate the variable under study as much as possible and included the use of selectively denervated preparations to limit contractions to specific muscles. It was found that altering the evoked tension by varying the resting muscle length had commensurate effects on the pressor reflex (greater evoked tension caused a larger reflex). In addition it was found that changing the amount of active muscle mass caused similar changes in the reflex (the smaller the muscle mass, the smaller the reflex). Finally, it was found that contrary to other accounts, pressor reflexes could be evoked by activation of the slow-twitch muscle soleus, composed exclusively of red (type I) fibers.

scholarly journals On the effect of the direction of external load application upon the change in stiffening behavior of rubber vibration isolators

2019 ◽  
Vol 109 ◽  
pp. 00053
Author(s):  
Mykola Lysytsia ◽  
Hennadii Ahaltsov ◽  
Natalia Lysytsia ◽  
Alina Novikova
Keyword(s):  
External Load ◽  
Experimental Results ◽  
Load Application ◽  
Vibration Isolators ◽  
Area Of Application

The paper represents experimental results concerning determination of stiffening behavior of rubber vibration isolators depending upon the direction of external load application as well as fastening conditions. Paying attention to the fastening technique makes it possible not only to widen the area of application for vibration isolators, but to reduce the range of the ones being manufactured.

scholarly journals High Resolution Determination of Body Segment Inertial Parameters and Their Variation Due to Soft Tissue Motion

2001 ◽  
Vol 17 (4) ◽  
pp. 326-334 ◽  
Author(s):  
Matthew T.G. Pain ◽  
John H. Challis
Keyword(s):  
Soft Tissue ◽  
Plantar Flexion ◽  
Accurate Method ◽  
Muscular Contraction ◽  
Lower Leg ◽  
The Body ◽  
Triceps Surae ◽  
Body Segment ◽  
Inertial Parameters

This study had two purposes: to evaluate a new method for measuring segmental dimensions for determining body segment inertial parameters (BSIP), and to evaluate the changes in mass distribution within a limb as a consequence of muscular contraction. BSIP were calculated by obtaining surface data points of the body under investigation using a sonic digitizer, interpolating them into a regular grid, and then using Green’s theorem which relates surface to volume integrals. Four skilled operators measured a test object; the error was approximately 2.5% and repeatability was 1.4% (coefficient of variation) in the determination of BSIP. Six operators took repeat measures on human lower legs; coefficients of variation were typically around 5%, and 3% for the more skilled operators. Location of the center of mass of the lower leg was found to move up 1.7 cm proximally when the triceps surae muscles went from a relaxed state to causing plantar flexion. The force during an impact associated with such motion of the soft tissue of the lower leg was estimated to be up to 300 N. In summary, a new repeatable and accurate method for determining BSIP has been developed, and has been used to evaluate body segment mass redistribution due to muscular contraction.

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